[web-devel] Automatically making every Cereal.Serialize instance of PersistField - bad idea?

[Max Cantor]

I should have added, as long as the type-checker terminates and doesn't go into an infinite loop, is there any danger in doing this?

On Jan 28, 2011, at 2:24 PM, Max Cantor wrote:

> With a bit of code, you can save a lot of effort if you add new types to Persistent:
> 
> instance Cereal.Serialize a => PersistField a where
>  toPersistValue a = PersistByteString $ Cereal.encode a
>  fromPersistValue (PersistByteString b) = Cereal.decode b
>  fromPersistValue _ = Left "bad type for cereal encoded data"
>  sqlType _ = SqlBlob
>  isNullable _ = False
> 
> BUT, this requires UndecidableInstances.  Is this a bad idea?
> 
> mc